Atomic Layer Deposition of High-Density GeSe Films for Stable Vertical Ovonic Threshold Switching and Selector-Only Memory

A thermally robust atomic layer deposition (ALD) process for binary GeSe is presented for vertically integrated chalcogenide electronic devices. By combining a GeIIN(CH3)2[N(iC3H7)2CN(CH3)2] precursor with [(CH3)3Si]2Se and NH3, stoichiometric GeSe growth is achieved up to 170 °C, extending the practical thermal window of GeSe ALD. A higher deposition temperature results in denser, more chemically ordered amorphous GeSe with markedly decreased C, N, and O impurities while preserving excellent conformality in high-aspect-ratio structures, thereby improving device performance. Vertical ovonic threshold switch devices with a TiN bottom electrode and C/Mo top electrode exhibit 40 ns turn-on and turn-off times, OFF-state leakage in the 10–8 A range, ON/OFF current selectivity above 103, and stable threshold switching over more than 5 × 105 cycles with narrow variation in threshold voltage and OFF-state current. The same vertical binary GeSe device also enables vertical selector-only memory performance via a polarity-dependent threshold-voltage shift, maintaining a memory window above 0.7 V for 2 × 105 cycles. High-temperature ALD-grown binary GeSe, therefore, provides a promising thin film material for vertically integrated selectors and single-layer selector-memory devices.